I can lock in my debt rate for 10,12,15 or 35 years on apartments (can't do that on other asset classes).Keep an eye on the spread between the 10yr treasury bond and the general cap rates for say multifamily.

Even if you never buy another property and just slowly pay down your existing debt (or not) the benefits of rental appreciation alone will take care of you.  

At one lender, he indicated that my debt-to-income ratio is too high, since I currently have three loans (primary residence and two investment properties, one of which I'd sell and 1031).My income is fairly high, and due to a job change, it's recently increased $20k. 

AKA the actual rate of return on a property you are feeding will generally be poor and you would be better off with a better cash flowing rental or in the stock market.Of course, if you found a great appreciating market or structured the debt to be shorter term, feeding a rental could work out well.

If not what are you figuring for debt service?

They will look for experience though, as well as your debt to income ratio, W-2 income, and any other assets you may have. 

How much and what kind of debt do I have?

However, banks can call the note in times of extreme circumstances so be aware of the risk and conservative in your debt management, liquidity, etc.    

You are young, park a camper on your land for 6 months or so and use the saving from rent to pay off debt or save itthen start looking at investment property

You are also $150k in debt, not $100k.